1. Field of the Invention
The instant invention relates to a method of and an apparatus for producing a gas-solid two phase flow jet having a constant mass or volume flow rate and predetermined velocity, in which free jet the solid particles are dispersed completely and uniformly.
2. The Prior Art
Feeding or metering dispersing devices are needed to generate gas-solid two phase flow jets of constant mass or volume flow rate wherever the dry processing of fine particle deposits requires that first these particles be picked up mechanically and then supplied or fed at constant mass or volume flow rate to a unit operation for which it is a condition that the particles be dispersed in defined manner. Examples of corresponding technical usage are the loading of wind sifters, the generation of gas-solid two phase flows, the measuring of particle size distributions based on the analysis of field effects in the gas-solid free jet, mechanical coating processes with which, for instance, a gas-solid jet is to be supplied at predetermined mass flow rate and fixed particle velocities to a surface which is prepared for a melt coating procedure, and the production of test aerosols. Production of the latter is much more sophisticated than the production of technical aerosols by conventional aerosol generators. The significant difference lies in the high mass flow rate required which is much higher for the applications described than the mass flow rate obtained with the known aerosol generators. To disperse fine solid particles which have agglomerated, it is attempted to disintegrate the agglomerates by forces of flow, particle-particle impacts, and particle-wall impacts. In the known dispersing means the material is subjected to all these stresses at the same time, but to different degrees.
The particle size range requiring measures to be taken for dispersing the particles begins approximately at 50 .mu.m. As the particles become finer, the measures become more sophisticated because the forces of adhesion acting among the particles increase at decreasing particle size. At particle sizes below 10 .mu.m full dispersion and disintegration of the particles become especially difficult.
Thus it is impossible to produce gas-solid particle free jets of constant mass or volume flow rate with the known metering dispersing devices if the solid particle size is below approximately 50 .mu.m.